Prolongations of the Fundamental Structure (Interruption)
The interruption is the most common way of prolonging the fundamental structure. The descent is interrupted and returns to the note on which it began before it is completed.

Interruption only occurs after and must return to the primary tone ( or ).

The interruption normally represents the end of a major section of a piece of music. The most familiar example is that of sonata form. The table below shows one example of how a sonata form movement might follow the principle of interruption: